Blue light grey. With the metallic luster of black powder. Insoluble in water, Xylene, slightly soluble in Pyridine for blue, brown light red fluorescence. In concentrated sulfuric acid to dark purple. Alkaline reduction leuco for red light blue; Acid reduction leuco for red light brown. Mainly used for cotton, vinylon, viscose fiber, and fabric dyeing and printing, and can also be used to dark gray discharge printing.